The present invention relates generally to spray nozzles, and more particularly to full cone liquid spray nozzles having particular utility for spraying liquid coolants in metal casting operations.
In metal casting operations, and particularly continuous metal casting systems in which steel slabs, billets, or other metal shapes are extruded from a mold, it is necessary to spray the emerging metal with water for rapid heat removal. It is desirable that the spray be finely atomized and uniformly directed onto the metal for uniform cooling. Uneven distribution of the liquid coolant results in non-uniform cooling of the metal, which can cause cracking, high stresses, and reduced surface and edge quality.
Full cone liquid spray nozzles have been used in continuous metal casting operations for directing cooling liquid, namely water, onto the metal surface for maximum cooling without dissolution by pressurized air. Prior full cone spray nozzles typically comprise a nozzle body having a discharge orifice and an upstream vane for imparting swirling movement to the liquid passing through the nozzle for breaking up the liquid flow and distributing liquid particles throughout the discharging conical spray pattern. Prior full cone spray nozzles, however, have had operating drawbacks.
One problem with prior full cone liquid spray nozzles arises by reason of the liquid throughput being controlled entirely by the liquid pressure. To achieve proper cooling, the volume of liquid sprayed in a continuous casting operation must be commensurate with the rate at which the steel shape is cast. In other words, when the metal emerges from the mold at a higher rate, a greater quantity of coolant is required for proper cooling than during lower rate casting. In prior full cone spray nozzles, however, a change in liquid pressure necessary for changing the spray volume also changed the angle of the discharging conical spray, which in turn changed the spray coverage, i.e. the area on the metal surface upon which the liquid impinges. A change in the spray coverage, in turn, can alter the uniformity in cooling by changing the extent discharging sprays of adjacent nozzles overlap, and in some cases, causing gaps between the discharging sprays of adjacent nozzles.
A further problem with the use of prior full cone liquid spray nozzles in continuous metal casting operations is that the discharging spray, regardless of spray pressure, is inherently non-uniform. Tests demonstrate that the volume of liquid collected per unit area (i.e. liquid density) along one narrow planar segment parallel to the axis of the spray nozzle varies substantially from the liquid density taken in a second narrow planar segment through the nozzle axis perpendicular to the first. While such non-uniformity might be taken into account if the spray nozzles could be mounted in predetermined relation to each other, typically the spray nozzles are simply screwed onto a supply pipe such that the irregular spray pattern of one nozzle has no relation to the irregular spray pattern of an adjacent nozzle, which can result in further non-uniformity in cooling of a moving cast metal.
It is an object of the present invention to provide a cast metal liquid spray system having full cone liquid spray nozzles adapted for more uniform liquid spraying, and hence, more uniform cooling of the metal.
Another object is to provide a full cone liquid spray nozzle in which the liquid spray volume of the discharging spray may be readily changed, according to the speed of the metal casting operation, without adversely affecting uniformity in cooling.
A further object is to provide a full cone spray nozzle as characterized above in which the discharging conical spray angle, and hence spray coverage, is substantially unaffected by changes in liquid pressure.
Yet another object is to provide a full cone liquid spray nozzle of the above kind in which liquid density in the discharging spray is substantially similar throughout the spray pattern, including planar segments through the axis of the nozzle perpendicular to each other.
Still another object is to provide a full cone liquid spray nozzle of the foregoing type which is relatively simple in construction and which lends itself to economical manufacture and reliable use.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: